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Abstract
Lithium ion batteries (LIBs) have grabbed increasing attention because they are the dominant power sources for most of portable electronics and the promising power sources for electric vehicles. Spinel lithium titanium, Li4Ti5O12 (LTO), has attracted significant attention as an alternative anode material for LIBs due to its unique properties such as high safety, long life time, easy fabrication, low cost and environmentally benignity. This work mainly focuses on the synthesis of LTO, LTO coupled with titanium dioxide (TiO2), and carbon-doped LTO materials (C-LTO) with morphology, size and function control. Four chapters are included in this thesis. In Chapter 1, the current research activities and developments of spinel LTO in the past years are summarized. Chapter 2 represents the synthesis of hollow structured LTO microspheres, followed by doping with TiO2 in LTO described in Chapter 3 and by modification using graphitized carbon in LTO discussed in Chapter 4. To obtain such materials, hydrothermal/solvothermal synthesis approaches were developed at 140-180 oC, followed by subsequent high-temperature calcination (500 oC) process for the spinel LTO materials. A number of advanced characterization techniques including SEM, TEM, HRTEM, SAED, XRD and Raman spectra are used to characterize the morphology and composition of the as-prepared LTO. The electrochemical measurements in terms of rate capability, charge-discharge profile and cycling performance are employed to evaluate the battery performance of LTO as an anode material. The results show that self-assembled LTO hollow microsphere is a promising anode material for high-power lithium-ion batteries. Modification of LTO by graphitic carbon doping enhances the capacity to 178 mAh/g at 10 C and can sustain a capacity of 169 mAh/g even after 100 cycles. LTO/TiO2 composite anode material can meet the high power requirement for large scale application, such as electric vehicles and energy storage systems based on desirable advantages of electrode materials.